Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology A-level OCR Yr13 > Genetics > Flashcards

Genetics Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

what is a mutation?

A

a change in the sequence of bases in DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Gene mutations are caused by?

A

substitution, deletion or insertion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is a point mutation

A

mutation affecting one nucleotide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In gene mutations, describe substitution?

A

the substitution of a single nucleotide changes the codon in which it occurs. If the new codon codes for a different amino acid, it will change the primary structure of the protein. However the codon’s degenerate nature may mean the new codon may not affect the primary structure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do amino acids impact the function of the protein?

A

the positions and involvement of the R-groups in amino acids impact the structure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe frame shift?

A

insertion or deletion of a nucleotide can cause a frame shift mutation. As each triplet is transcribed in groups of three consecutively, all subsequent codons from the point mutation is altered.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How will the deletion or insertion of many nucleotides affect the protein?

A

a frame shift mutation is still seen with multiple insertions or deletions. However if multiples of three correspond to full codons, the reading frame will not be changed but will still affect the protein as a new protein is added

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the effects of different mutations?

A

-no effect: normally functioning proteins are still synthesised
-damaging: protein is not synthesised of non-functional
-beneficial: protein synthesised with useful characteristic in phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is a mutagen?

A

chemical, physical or biological agent which causes mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the causes of mutations?

A

they occur spontaneously but the rate is increased by mutagens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how does depurination and depyrimidation affect mutations?

A

absence of base can lead to insertion of incorrect base through complementary base pairing during DNA replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

describe free radicals?

A

oxidising agents which can affect the structure of nucleotides and base paring in DNA replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why are antioxidants (e.g vitamin A, C, E) known as anticarcinogens?

A

because of their ability to negate the effects of free radicals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are the main types of mutagen?

A

physical mutagen, chemical mutagen and biological agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe physical mutagens?

A

e.g ionising radiation (X-rays) cause breakage of one or two DNA strands, mutations can occur in the process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe chemical mutagens?

A

e.g deaminating agents which chemically alter bases in DNA, changing the base sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe biological agents?

A

-e.g alkylating agents: methyl or ethyl groups attached to bases can result in incorrect base pairing
-e.g base analogs: incorporated into DNA in place of the unusual base during replication, changing base sequence
-e.g viruses: viral DNA can insert itself into genome, changing base sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe silent mutations?

A

-doesn’t affect protein function
-due to the degenerate nature of codons or the point mutation may have occurred in the non-coding regions of DNA
-changes primary structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

describe a nonsense mutation?

A

mutation causing codon to become stop codon instead of coding for another amino acid- shortened protein which is usually non-functional.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe a missense mutaion?

A

mutation as a result of the incorporation of the incorrect amino acid. Mutation can be silent, beneficial or harmful depending on the amino acid properties compared to the original one.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are chromosome mutations?

A

mutations affecting whole chromosome which is also caused by mutagens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

changes in chromosome structure include?

A

-deletion: a section of chromosome breaks off and is lost within the cell
-duplication: sections get duplicated on a chromosome
-translocation: a section of one chromosome breaks off and joins another non-homologous chromosome
-inversion: a section of chromosome breaks off, is reversed, and then joins back onto the chromosome.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

In what ways can genes be regulated?

A

-transcriptional: genes can be turned on or off
-post-transcriptional: mRNA can be modified which regulates translation and the types of proteins produced
-translational: translation can be stopped or started
-post-translational: proteins can be modified after synthesis which changes their functions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is heterochromatin?

A

tightly wound DNA causing chromosomes to be visible during cell division. This doesn’t allow transcription to occur.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is euchromatin?

A

loosely wound DNA present during interphase. This allows transcription to occur.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What occurs during interphase?

A

protein synthesis- proteins necessary for cell division are synthesised which prevents energy-consuming process of protein synthesis during division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How does DNA coil around histones

A

DNA is negatively charged and histones are positively charged

28
Q

how is a euchromatin produced?

A

the addition of an acetyl group (acetylation) or phosphate group (phosphorylation). This reduces the positive charge on the histones causing DNA to coil less tightly

29
Q

how is a heterochromatin produced?

A

the addition of a methyl group (methylation) makes histones more hydrophobic so they bind more tightly to each other causing DNA to coil more tightly.

30
Q

What is epigenetics?

A

the control of gene expression by the modification of DNA.

31
Q

what is an operon?

A

group of genes that are under the control of the same regulatory mechanism and are expressed at the same time.

32
Q

where are operons commonly found?

A

In simpler and smaller genomes of prokaryotes

33
Q

In E.coli, what occurs when glucose is in short supply?

A

lactose can be used as a respiratory substrate. Different enzymes are needed to metabolise lactose.

34
Q

What are the structural genes involved in the metabolism go lactose?

A

lacZ, lacY and lacA. Structural genes are genes which code for proteins not involved in DNA regulation. These structural genes are code for three enzymes (B-galactosidase, lactose permease and transacetylase).

35
Q

Describe the regulatory gene

A

Regulatory gene codes for proteins involved in DNA regulation. The LacI gene codes for the repressor protein. Repressor protein prevents transcription of structural genes in the absence of lactose.

36
Q

what is the operator region of the lac operon?

A

DNA sequence where repressor protein binds to

37
Q

what is the promoter region of the lac operon?

A

DNA sequence where RNA polymerase bind to

38
Q

What happens when the repressor protein binds to the operator region?

A

prevents RNA polymerase binding to promoter region

39
Q

What occurs when lactose is present?

A

lactose binds to the repressor protein causing it to change shape, making it no longer bind to the operator. Therefore RNA polymerase can bind to the promoter region. The three structural genes are transcribed and enzymes are synthesised.

40
Q

How is the rate of transcription increased?

A

cAMP receptor protein (CRP) binds to cyclic AMP (cAMP). This complex binds to RNA polymerase.

41
Q

What is the structure of the lac operon

A

LacI, operator, promoter, LacZ, LacY, LacA

42
Q

how does the transport of glucose into an E.coli cell affect levels of cAMP?

A

decreases levels of cAMP, reducing transcription of genes responsible for the metabolism of lactose. If both glucose and lactose are present then it will still be glucose as the preferred respiratory substrate that is metabolised.

43
Q

What happens during post-transcriptional control (pre-mRNA to mature mRNA)?

A

-Introns are spliced out of the pre-mRNA
-A cap (modified nucleotide) is added to the 5’ end and a tail (a chain of adenine nucleotides) is added to the 3’ end
-this occurs in the nucleus

44
Q

What are introns and extrons?

A

introns- non-coding DNA
extrons- coding DNA

45
Q

Why is a cap and tail added to the pre-mRNA?

A

-stabilise mRNA
-delay degradation in the cytoplasm
-cap aids binding of mRNA to the ribosomes

46
Q

what is translational control?

A

translational control is switching translation on and off. Down regulating translation can occur degradation and binding of inhibitory proteins. Up regulation of translation can occur by activating initiation factors.

47
Q

Describe the affect of binding inhibitory proteins to mRNA in translational control?

A

it prevents binding to ribosomes and synthesis of proteins

48
Q

Describe the effect of activating initiation factors in translational control?

A

aids the binding to ribosomes

49
Q

describe protein kinases?

A

enzymes that catalyse the addition of a phosphate groups to proteins. This addition changes the tertiary structure and so function of the protein. Many enzymes are activated by phosphorylation. Protein kinases are activated by secondary messengers, cAMP.

50
Q

Post-translational control includes?

A

-addition of non-protein groups such as carbohydrate chains, lipids or phosphates
-modifying amino acids and the formation of bonds such as disulphide bridges
-folding or shortening proteins
-modification of cAMP

51
Q

What are homeobox genes?

A

regulatory genes which all contain homeobox.

52
Q

what is a homeobox?

A

section of DNA 180 base pairs long coding for a part of the protein 60 amino acids long that is highly conserved (very similar in plants, animal and fungi). This part of a protein, a homeodomain, binds to DNA and switches other genes on or off.

53
Q

Describe hox genes (homeobox genes)?

A

responsible for the correct positioning of body parts. They are found in gene clusters in animals. The order in which the genes appear along the chromosome is the order in which their effects are expressed.

54
Q

Describe somites

A

-individual vertebrae and associated structures have all developed from segments in the embryo called somites
-somites are directed by hot genes to develop in a particular way depending on their position in the sequence.

55
Q

Describe radial symmetry

A

seen in diploblastic animals like jellyfish. They have no left or right sides, only a top or bottom

56
Q

Describe bilateral symmetry

A

seen in most animals means the organisms have both left and right sides and a head and tail rather than just a top and bottom

57
Q

Describe asymmetry

A

no lines of symmetry

58
Q

Describe apoptosis

A

-term for normal, regulated cell death (programmed cell death)
-occurs at the same rate as cell division
-it can occur during development to shape an organisms features

59
Q

How does apoptosis shape an organism’s features?

A

-by removing unwanted cells and tissues
-releasing chemical signals which stimulate mitosis and cell proliferation

60
Q

what is necrosis?

A

name for cell death due to injury or illness

61
Q

How are apoptosis and how genes linked?

A

hox genes, in their role as transcription factors , turn on and off the genes for the proteins which lead to apoptosis in developing organisms

62
Q

The expression of regulatory genes is influenced by what?

A

-influenced by stress
-drugs

63
Q

Describe the methylation of DNA

A

increased methylation of DNA inhibits transcription. When the methyl group (positive) are added to DNA, they attach to cytosine base. This prevents transcriptional factors from binding and attracts the proteins which condense the DNA- histone complex, preventing transcription

64
Q

Describe acetylation of histone proteins

A

Decreased acetylation of the associated histones proteins on DNA inhibits transcription. If acetyl groups are removed from the DNA then the histones become more positive and are attracted more to the phosphate group on DNA. This strong association prevents transcription factors from binding

65
Q

what is alternative splicing?

A

mRNA is spliced into many different ways allowing a single gene to create multiple proteins

Biology A-level OCR Yr13 (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions